1. Field of the Invention
The present invention generally relates to linear actuators and, in particular to a linear actuator device with a speed-adjustable quick release mechanism.
2. Description of Prior Art
A linear actuator usually uses driving components such as an electric motor, a worm shaft and a worm gear etc. to drive a lead screw rotating. Meanwhile, a telescopic tube screwed with the lead screw will perform a linear extend or retract motion with respect to an outer tube sleeved on the telescopic tube. Because the linear actuator has a simple and convenient structure and installation with respect to gas or hydraulic cylinders, the linear actuator is widely applied in hospital beds, electrical chairs and other medical devices and equipments or other fields which a telescopic motion is needed.
Take a linear actuator applied for adjusting a hospital bed for example, such as Taiwan Utility Model NO. M275836 with title “A quick release mechanism of a hospital bed actuator”. The patent discloses a hospital bed with an actuator for tilt controlling. The actuator has a telescopic tube connecting with an adjustment frame of the hospital bed. The telescopic tube is inserted in an outer tube, and the telescopic tube is sleeved on a lead screw. The lead screw also sleeves with a worm gear and a spring. The quick release mechanism has a pressing pole disposed between the lead screw and the worm gear. The telescopic tube rotates downward rapidly by actuating the pressing pole to pull the worm gear and the lead screw apart for achieving a quick release of the hospital bed.
The above quick release mechanism can be functioned to make a hospital bed back to its original position quickly for an immediately treatment in an emergency or a power outage situation. However, if the quick release for returning a hospital bed back to its original position is performed in a power outage situation, a large impact makes a patient discomfort. Hence, how to develop a speed-adjustable quick release mechanism is an object of the inventor.
In view of the above drawbacks, the Inventor proposes the present invention based on his expert knowledge and elaborate researches in order to solve the problems of prior art.